Tornado Warning 23, NWS Hastings, NE

SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
250 PM CDT SUN MAY 2 1999

MAIN CONCERN FOR THIS FORECAST PACKAGE WILL BE TIMING OF SHOWERS
ENDING/DRY SLOT ENTERING AS WELL AS POPS MON NITE AND TUES. WV SATL
PIX THIS AFTN SHOWING UPPER LEVEL LOW SPINNING OVER NE CO/SW NEB AND
SHOULD CONTINUE TO MIGRATE NE THRU THE PERIOD. A QUICK LOOK AT VIS
SATL SHOWING EXTENSIVE CLEARING FROM SW KS SOUTHWARD INTO THE OKLA
PANHANDLE AND INTO WRN TX AS LATEST 700MB PROFILERS INDICATING DRY
DOWNSLOPING AIR ADVECTING INTO THIS REGION. MEANWHILE LATEST SFC
ANALYSIS HAS A TROF OF LOW PRESSURE EXTENDING SOUTHWARD FROM SFC
LOW PRESSURE OVER SRN CANADA. A RELATIVELY TIGHT GRADIENT ACROSS
THE PLAINS IS KEEPING WINDS MOSTLY OUT OF THE SE WITH GUSTS TO
AROUND 30KTS. INITIALIZATION OF THIS MORNINGS MODEL RUN SHOWED A FEW
DIFFERENCES IN DETAILS PARTICULARLY WITH 850MB TEMPS. ALL MODELS
ARE SOMEWHAT UNDERESTIMATING EXTENT OF WAA RIDING ALONG SOUTHERLY
FLOW WITH THE ETA APPEARING TO HAVE THE BEST HANDLE ON THE
SITUATION. WILL GENERALLY FOLLOW ETA SOLN FOR FIRST COUPLE PERIOD AND
BLEND AFTERWARD. A COMPARISON OF THE LAST COUPLE OF ETA RUNS
INDICATE ITS BEEN A BIT TOO FAR SOUTH WITH THIS SYSTEM...BUT HAS COME
INTO LINE AND SEEMS TO BE IN DECENT AGREEMENT WITH LATEST WV LOOP
IMAGE AND RUC RUN. THE NGM AND AVN ON THE OTHER HAND HAVE BEEN KIND
OF WEAK AND UNDERESTIMATED VORT STRENGTH. FOR TONITE PCPN SHOULD MOVE
OUT OF THE CWA AS DRY AIR ADVECTS INTO AREA WITH SOME PARTIAL
CLEARING EXPECTED LATE IN MOST PLACES WITH WINDS REMAINING AT 15/25.
WILL GO SLIGHTLY BELOW MOS GUIDANCE FOR LOWS TONITE. MON LOOKING TO
BE A NICE DAY AS DRY TROP AND GOOD WAA MOVES IN ALONG SOUTH WINDS OF
20/30. BY LATE AFTN ETA BECOMES AGGRESSIVE WITH INSTABILITIES OVER
ERN CWA AND ERN NEB. THE ETA MAY BE OVERESTIMATING AMOUNT OF BNDRY
LYR MOISTR ADVECTING IN FROM SOUTH AS MIXING RATIO VALUES JUMP FROM
AROUND 9 G/KG TO OVER 12 G/KG BY DAYS END WHILE THE NGM PLACES HIER
MOISTR VALUES OFF TO THE EAST. NEVER THE LESS WILL GO SLIGHTLY ABOVE
MOS GUIDANCE FOR AFTN HIGHS OVER THE CWA CONSIDERING THE AMOUNT OF
WAA. CLOUDS ON THE INCRS MON NITE AS NEXT SYSTEM MOVES ACROSS THE
ROCKIES AND INTO THE PLAINS. WILL GO WITH SMALL POPS TO COVER ANY
LATE PERIOD PCPN. MOS NUMBERS LOOK REASONABLE AND WILL FOLLOW. ON
TUESDAY UPPER LVL SYSTEM BECOMES MORE ENTRENCHED OVER REGION AS SFC
COLD FRONT IS PROGGED THRU THE CWA SOME TIME DURING THE LATE
MORNING/EARLY AFTN AS PER AVN...AND WILL THEREFORE UNDERCUT MOS TEMPS
A BIT. AVN PROGS ADEQUATE MOISTR AND INSTABILITY AND AT THIS POINT
FEEL COMFORTABLE ENOUGH TO GO WITH LIKELY POPS WITHIN NEB PORTION OF
CWA.

.GID...NONE

DEE